Liquid crystal device and electronic equipment

ABSTRACT

A liquid crystal device has a structure in which an electric field is applied across a liquid crystal in a direction substantially parallel to the plane of a substrate. A conductive film is formed on a first substrate on which an electric field control is provided, and also on a color filter substrate located opposite the first substrate, and the conductive films are maintained at either a ground voltage, a common electrode voltage, the center voltage of an image signal, a non-selection voltage of a scanning signal, or a logic voltage of an external driver or otherwise the voltage of the conductive films is maintained in a floating state. The liquid crystal device having the above structure displays a high-quality image without encountering an influence of electrostatic charges.

TECHNICAL FIELD

[0001] The present invention relates to an active matrix type liquidcrystal device including active elements located at respective pixels(also called picture elements) thereby controlling the voltage appliedto the liquid crystal at the respective pixels, and more particularly,to a liquid crystal device of the type in which a voltage is applied ina lateral direction (along the layer) to the liquid crystal at therespective pixels.

[0002] The present invention also relates to electronic equipment usingsuch a liquid crystal device.

BACKGROUND ART

[0003] The great majority of liquid crystal devices used in notebookpersonal computers or liquid crystal TV sets are operated in the twistednematic mode. However, in the twisted nematic mode, the image displayedon a liquid crystal device looks different depending on the viewingdirection. To improve the viewing direction dependence, it has beenproposed to employ an in-plane switching (IPS) mode in which a voltageis applied to a liquid crystal in a lateral direction, as disclosed forexample in Japanese Unexamined Patent Publication Nos. 56-091277 and6-160878.

[0004] The principle of operation in the IPS mode will be describedbriefly with reference to some drawings. FIGS. 4a and 4 b arecross-sectional views illustrating the behavior of a liquid crystal in aliquid crystal panel designed to operate in the IPS mode, wherein FIG.4a is a cross-sectional view of a cell without an application of voltageand FIG. 4b is a cross-sectional view of the cell under the applicationof a voltage greater than a threshold value. The plane views of FIGS. 4aand 4 b are given in FIGS. 4c and 4 d, respectively. In FIG. 4,reference numerals 401 and 409 denote a pair of polarizing plates, 402and 408 denote a pair of substrates between which a liquid crystal isdisposed, 403 denotes a color filter, 404 and 406 denote orientatingfilms, and 405 denotes a liquid crystal molecule drawn in a schematicfashion. Furthermore, reference numeral 410 denotes a pixel electrode,411 denotes a common electrode disposed in a pixel at a locationopposite to the pixel electrode, 412 denotes an image signal line(source line), and 407 denotes an insulating layer for isolating thepixel electrode 410 and the common electrode 411 from each other. In theIPS-mode liquid crystal device, as can be seen from FIG. 4, the pixelelectrode and the common electrode for applying a voltage across theliquid crystal are disposed on one substrate at locations apart in alateral direction. Reference numeral 413 denotes the absorption axis ofthe lower polarizing plate and 414 denotes the absorption axis of theupper polarizing plate.

[0005] Although an active element such as a TFT (thin film transistor)is also disposed, it is not shown in FIG. 4. FIGS. 4a and 4 b are across section taken along line X-X′ of FIG. 5, and FIGS. 4c and 4 d arean enlarged plane view illustrating an area surrounded by a broken linein FIG. 5, wherein FIG. 5 illustrates the structure of one pixel. In thespecific example shown in FIG. 5, two common electrodes 502 and onepixel electrode 501 are disposed in a lateral direction in one pixel,whereas there may be some other number of common electrodes 502 andpixel electrodes 501 in one pixel. Furthermore, in FIG. 5, referencenumeral 503 denotes a scanning signal line (gate line), 504 denotes animage signal line (source line), and 505 denotes a thin filmtransistor(TFT).

[0006] Of the pair of substrates 402 and 408, as shown in FIGS. 4a and 4c, a color filter 403 is formed on the upper substrate 402, and aline-shaped common electrode 411 and pixel electrode 410 are formed onthe inner surface of the lower substrate 408. Furthermore, orientatingfilms 404 and 406 for orientating the liquid crystal molecules 405 areformed on the inner surfaces of the respective substrates. A liquidcrystal is disposed between the pair of substrates 402 and 408. When novoltage is applied, the liquid crystal molecules 405 are uniformlyorientated at a fixed angle (within the range from 0 to 45) with respectto the longitudinal direction of the line-shaped electrodes (commonelectrode 411, pixel electrode 410). In the specific example shown inFIG. 4, the angle is set to 30°. On both sides of the liquid cell, thereare disposed polarizing plates 401 and 409. The upper polarizing plate401 is disposed such that its absorption axis 414 becomes parallel tothe orientation of the liquid crystal. On the other hand, the lowerpolarizing plate 409 is disposed such that its absorption axis 414becomes perpendicular to the orientation of the liquid crystal. In thisstate, black is displayed in the pixel. The liquid crystal is made up ofa material having positive dielectric anisotropy.

[0007] If an electric field 415 is applied, the liquid crystal molecules405 are aligned so that their longitudinal axis is directed in adirection parallel to the electric field 415, as shown in FIGS. 4b and 4d. As a result, the orientation of the liquid crystal molecules 405 cometo have a certain angle with respect to the absorption axis of thepolarizing plates. The birefringence of the liquid crystal varies inaccordance with the orientation angle of liquid crystal molecules whichvaries in response to the strength of the applied electric field. Thus,it is possible to control the transmission of light through the pair ofpolarizing plates thereby controlling the brightness.

[0008] In this structure, however, the pixel electrode 410 and thecommon electrode 411 used to apply a voltage across the liquid crystalare formed on only one substrate and there is no electrode on theother-side substrate. This can cause a problem in that the substratetends to be electrostatically charged. The electrostatic charge disturbsthe orientation of the liquid crystal and thus it becomes impossible todisplay a high-quality image. Once the substrate is electrostaticallycharged, it is difficult to remove the electrostatic charge becausethere is no electrode on the other-side substrate.

[0009] In view of the above, it is an object of the present invention toprovide a liquid crystal device capable of displaying a high-qualityimage without being electrostatically charged or without beinginfluenced by an electrostatic charge.

DISCLOSURE OF INVENTION

[0010] According to an aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a light-shielding metal film isformed on the other-side substrate opposite to the one of the substrate,and a fixed voltage is applied to the light-shielding metal film.

[0011] In this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. If there were no light-shielding metal film disposedon the other-side substrate and maintained at the fixed voltage, thesubstrate would be electrostatically charged, and as high a voltage as afew ten thousand volts would occur between the other-side substrate andthe pixel electrodes and/or the common electrode formed on the onesubstrate. The liquid crystal would response to that voltage. For theabove reason, to achieve a high-quality image, it is important that thelight-shielding metal film be formed on the other-side substrate havingno electrode for driving. the liquid crystal and be maintained at afixed voltage. Preferably, the light-shielding metal film is made up ofchromium (Cr) or a nickel-copper (Ni—Cu) alloy.

[0012] According to another aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a transparent conducting film isformed on the other-side substrate opposite to the one of thesubstrates, and a fixed voltage is applied to the transparent conductingfilm.

[0013] With this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. If there were no transparent conducting filmdisposed on the other-side substrate and maintained at the fixedvoltage, the substrate would be electrostatically charged, and as high avoltage as a few ten thousand volts would occur between the other-sidesubstrate and the pixel electrodes and/or the common electrode formed onthe one substrate. The liquid crystal would response to that voltage.For the above reason, to achieve a high-quality image, it is importantthat the transparent conducting film be formed on the other-sidesubstrate having no electrode for driving the liquid crystal and bemaintained at a fixed voltage. Preferably, the transparent conductingfilm may be made up of ITO or tin oxide (SnO₂).

[0014] According to another aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a conductive film is formed onthe other-side substrate opposite to the one of the substrates, in theperiphery of the pixel area on either the inner surface or the outersurface of the other-side substrate, and a fixed voltage is applied tothe conductive film.

[0015] With this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. If there were no conductive film disposed on theother-side substrate and maintained at the fixed voltage, the substratewould be electrostatically charged, and as high a voltage as a few tenthousand volts would occur between the other-side substrate and thepixel electrodes and/or the common electrode formed on the onesubstrate. The liquid crystal would response to that voltage. For theabove reason, to achieve a high-quality image, it is important that thelight-shielding metal film be formed on the other-side substrate havingno electrode for driving the liquid crystal and be maintained at a fixedvoltage. Since the conductive film is formed in areas outside thedisplaying areas, it is not required that the conductive film betransparent, and thus various metallic materials may be employed to formthe conductive film.

[0016] Herein, the pixel area refers to such an area in which an elementof an image such as a character or a picture is displayed. An example ofa pixel area is an area 303 of the liquid crystal cell denoted by abroken line in FIG. 3. The periphery of the pixel area refers to such anarea which is located outside the pixel area and which has no capabilityof displaying an image. In FIG. 3, reference numeral 304 denotes theperiphery of the pixel area.

[0017] Preferably, the fixed voltage is either a ground voltage, avoltage on the common electrode, the center voltage of the image signalamplitude, a non-selection voltage of the scanning signal, or a logicvoltage provided from an external driving means.

[0018] In this technique, a proper one of existing voltages in theliquid crystal device can be used without having to generate anadditional voltage, and thus it is possible to realize a liquid crystaldevice capable of displaying a high-quality image and having highresistance to electrostatic charge without causing an increase in cost.

[0019] Herein, the common electrode voltage, the center voltage of theimage signal amplitude, and the non-selection voltage of the scanningsignal refer to such voltages denoted by reference numerals 606, 605,and 607, respectively, in FIG. 6 representing the waveforms of drivingsignals associated with a liquid crystal panel with TFTs. The waveformsof the driving signals shown in FIG. 6 are described briefly below injunction with an equivalent circuit of a TFT shown in FIG. 7. Signals602 and 603 are supplied over a scanning line 703 and an imaging signalline 704, respectively, and applied to the gate and source,respectively, of the TFT 705. According to the NTSC standard, an imagesignal consists of two interlaced fields, that is, a first field 610 anda second field 611, which make up one frame 612 thereby making up onepicture. In a selection period 608, if the TFT 705 is turned on by aselection signal supplied via the scanning signal line 703, the voltage604 of the pixel electrode 701 becomes nearly equal to the voltage 603of the image signal line 704. In a non-selection signal 609, the TFT 705is turned off and the signal written in a liquid crystal capacitor 706is held. The scanning signal lines 703 are selected one by one in asimilar manner so that data is rewritten once every one field for allpixels.

[0020] According to another aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a polarizing plate having anelectrical conductivity is disposed on the outer surface of theother-side substrate opposite to the one substrate, and a fixed voltageis applied to the polarizing plate.

[0021] In this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. If there were no conductive film disposed on theother-side substrate and maintained at the fixed voltage, the substratewould be electrostatically charged, and as high a voltage as a few tenthousand volts would occur between the other-side substrate and thepixel electrodes and/or the common electrode formed on the onesubstrate. The liquid crystal would response to that voltage. For theabove reason, to achieve a high-quality image, it is important that thepolarizing plate having an electrical conductivity be formed on theother-side substrate having no electrode for driving the liquid crystaland be maintained at a fixed voltage.

[0022] In the present invention, the above-described fixed voltage iseither a ground voltage, a voltage on the common electrode, the centervoltage of the image signal amplitude, a non-selection scanning signalvoltage, or a logic voltage provided from an external driving means.

[0023] According to another aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a transparent conducting film isformed on either the inner-side or outer surface of the other-sidesubstrate opposite to the one substrate and the voltage of thetransparent conducting film is maintained in a floating state.

[0024] In this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. Even if the liquid crystal device is partiallycharged, the transparent conducting film prevents the orientation of theliquid crystal from being locally disturbed, and the charge is relaxedover the conductive film. Furthermore, in this technique, since thevoltage of the transparent conducting film is maintained in a floatingstate, no electrical connection is required. In general, if thetransparent conducting film is formed on the inner surface of thesubstrate, that is, in the inside of a liquid crystal cell, a voltagedifference occurs between the transparent conducting film and the pixelelectrode and/or the common electrode. As a result, degradation in theimage quality occurs. However, in the present technique, since thevoltage of the conductive film is maintained in the floating state, thedegradation in the image quality is suppressed. Preferably, thetransparent conducting film is made up of ITO or tin oxide (SnO₂).

[0025] Herein, the floating state refers to such a state in which aconductive material is electrically isolated from any voltage inadjacent locations and thus the voltage of the conductive material is ina floating state.

[0026] According to another aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a conductive film is formed onthe other-side substrate opposite to the one of the substrate, in theperiphery of the pixel area on either the inner surface or the outersurface of the other-side substrate, and the voltage of the conductivefilm is maintained in a floating state.

[0027] In this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. Even if the liquid crystal device is partiallycharged, the transparent conducting film prevents the orientation of theliquid crystal from being locally disturbed, and the charge is relaxedover the conductive film. Furthermore, since the voltage of thetransparent conducting film is maintained in a floating state, noelectrical connection is required. Since the conductive film is formedin areas outside the displaying areas, it is not required that theconductive film be transparent, and thus various metallic materials maybe employed to form the conductive film.

[0028] According to another aspect of the present invention, there isprovided a liquid crystal device including a pair of substrates with aliquid crystal disposed between them, one of the substrates having,thereon, scanning signal lines and image signal lines disposed in amatrix form, active elements connected to the respective scanning signallines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each pixel electrode and the common electrode in such a mannerthat the electric field is applied in a direction substantially parallelto the plane of the substrates, wherein a polarizing plate having anelectrical conductivity is disposed on the outer surface of theother-side substrate opposite to the one substrate, and the voltage ofthe polarizing plate is maintained in a floating state.

[0029] In this structure, the other-side substrate is prevented frombeing electrostatically charged and thus it is possible to display ahigh-quality image. Even if the liquid crystal device is partiallycharged, the transparent conducting film prevents the orientation of theliquid crystal from being locally disturbed, and the charge is relaxedover the conductive film. Furthermore, since the voltage of thetransparent conducting film is maintained in a floating state, noelectrical connection is required.

[0030] In this structure according to the present invention, theconductive film is formed on the inner or outer surface of theother-side substrate thereby ensuring that the orientation of the liquidcrystal is maintained in a desired direction without encounteringdisturbance. Although the external electrostatic charge can be absorbedeven if the conductive film is formed on either the inner or outersurface of the other-side substrate, it is more preferable that theconductive film be formed on the inner surface of the other-sidesubstrate so that the electrostatic charge is absorbed at a locationnearer to the liquid crystal layer.

[0031] The liquid crystal device constructed in any form described abovemay be employed as a display device in various electronic equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a schematic diagram illustrating a liquid crystal deviceaccording to the present invention;

[0033]FIG. 2 is a cross-sectional view of the liquid crystal deviceaccording to the present invention;

[0034]FIG. 3 is a plane view of a liquid crystal cell according to thepresent invention;

[0035]FIG. 4 is a schematic representation of the IPS mode;

[0036]FIG. 5 is a schematic diagram illustrating one pixel of the liquidcrystal device according to the present invention;

[0037]FIG. 6 is a graph illustrating the waveforms of driving signalsused in a TFT type liquid crystal device;

[0038]FIG. 7 is a circuit diagram illustrating an equivalent circuit ofone pixel of the liquid crystal device according to the presentinvention;

[0039]FIG. 8 illustrates a liquid crystal cell in which electrodes onthe inner surfaces of the upper and lower substrates are electricallyconnected to each other via a silver paste, according to the presentinvention, wherein a plane view and an enlarged cross-sectional viewthereof are shown;

[0040]FIG. 9 is a cross-sectional view illustrating a liquid crystalcell in which electrodes on the inner surfaces of the upper and lowersubstrates are electrically connected to each other via a silver paste,according to the present invention;

[0041]FIG. 10 is a block diagram illustrating a driving circuit ofdriving a liquid crystal device, according to the present invention;

[0042]FIG. 11 is a schematic diagram illustrating a personal computerusing a liquid crystal device according to the present invention;

[0043]FIG. 12 illustrates an example of the structure of a pager using aliquid crystal device according to the present invention; and

[0044]FIG. 13 is a schematic diagram illustrating an example of apractical manner in which a liquid crystal device according to thepresent invention is mounted.

BEST MODE FOR CARRYING OUT THE INVENTION

[0045] The present invention will be described in further detail belowwith reference to the accompanying drawings.

[0046] (First Embodiment)

[0047]FIG. 1 is a schematic diagram illustrating a main part of a liquidcrystal device according to the present invention, wherein FIG. 1a is aplane view of a color filter substrate 104, and FIG. 1b is across-sectional view of the liquid crystal device. The structure isdescribed first. Two transparent glass substrates 104 and 109 with athickness of 1.1 mm are disposed in close proximity to each other, and aliquid crystal layer 106 is disposed between them. A light-shieldingchromium (Cr) film 101, a red/green/blue (RGB) color filter 102, and anorientating film 105 are formed one on another on the inner surface ofthe upper glass substrate 104, and a polarizing plate 103 is disposed onthe outer surface of the upper glass substrate 104. Common electrodes111, an insulating layer 108, pixel electrodes 112, and an orientatingfilm 107 are formed on the inner surface of the lower glass substrate109, and a polarizing plate 110 is disposed on the outer surface of thelower glass substrate 109.

[0048] As described earlier with reference to the plane view of thelower glass substrate shown in FIG. 5, scanning signal lines (gatelines) 503 and image signal lines (source lines) 504 extend in a matrixform across the respective pixels. Thin film transistors (TFTs) 505 areformed near the respective intersections of the scanning signal lines503 and the image signal lines 504, wherein the gate electrodes of therespective thin film transistors are connected to the correspondingscanning signal lines 503, the source electrodes to the correspondingimage signal lines 504, and the drain electrodes to the correspondingpixel electrodes 501 (112).

[0049] The light-shielding chromium film 101 shown in FIG. 1 is formedso as to shield, from light, the areas on the lower substrate in whichthe thin film transistors, the image signal lines, and the scanningsignal lines are formed.

[0050] As shown in FIG. 1, the common electrode 111 (502) and the pixelelectrode 112 (502) in one pixel are located in different layersseparated by the insulating layer 108. In FIG. 1, lines 113 denote thedirection of the electric field. In this specific embodiment, the upperand lower substrates were spaced by 4.5 μm, and a nematic liquid crystalhaving positive dielectric anisotropy and having anisotropy inrefractive index Δn=0.070 was employed as the liquid crystal material106. The line-shaped common electrodes 111 and the pixel electrodes 112were spaced by 10 μm wherein the width was set to 5 μm for bothelectrodes. A rubbing orientation process was performed so that thelongitudinal axes of the liquid crystal molecules were aligned at 30°with respect to the longitudinal direction of the line-shaped electrodes(common electrodes 111, pixel electrodes 112). The polarizing plate 103on the upper glass substrate 104 was disposed such that its absorptionaxis became parallel to the orientation of the liquid crystal. On theother hand, the polarizing plate 110 on the lower glass substrate 109was disposed such that its absorption axis became perpendicular to theorientation of the liquid crystal. In this state, black is displayed inthe pixel. The orientation angle of the liquid crystal molecules variesand thus the birefringence varies in response to a voltage applied fromexternal driving means. Thus, it is possible to control the brightnessby changing the applied voltage. Below the lower substrate 109, there isprovided a back light source. The manner in which the liquid crystalmolecules are orientated and the manner of setting the absorption axesof the polarizing plates are similar to those described above withreference to FIG. 4.

[0051] The light-shielding chromium film 101 shown in FIG. 1 is formedso as to shield, from light, the areas on the lower substrate in whichthe thin film transistors, the image signal lines, and the scanningsignal lines are formed.

[0052] Referring now to FIGS. 6 and 7, a method of driving the activematrix liquid crystal device is described below. FIG. 7 is a circuitdiagram illustrating an equivalent circuit of one pixel of the liquidcrystal device. FIG. 6 illustrates the waveform of driving signals. InFIG. 7, reference numeral 703 denotes a scanning signal linecorresponding to 503 in FIG. 5, reference numeral 704 denotes an imagesignal line corresponding to 504 in FIG. 5, and reference numeral 705denotes a thin film transistor corresponding to 505 in FIG. 5. The gateelectrode of the thin film transistor 705 is connected to the scanningsignal line 503, the source electrode is connected to the image signalline 704, and the drain electrode is connected to the pixel electrode701 corresponding to 501 in FIG. 5 (112 in FIG. 1). Reference numeral706 denotes a liquid crystal capacitor. Reference numeral 702 denotes acommon electrode corresponding to 502 in FIG. 5 (111 in FIG. 1). FIG. 6illustrates the signals for driving one pixel as a function of time. InFIG. 6, reference numeral 607 denotes a scanning signal applied over thescanning signal line, reference numeral 608 denotes a selection periodduring which the thin film transistor is turned on, and referencenumeral 609 denotes a non-selection period during which the thin filmtransistor is turned off and the liquid crystal is held at the voltageapplied in the previous selection period. During the selection period608, the image signal 603 supplied over the image signal line is appliedto the pixel electrode via the thin film transistor. Reference numeral612 denotes one frame period, reference numeral 610 denotes a firstfield, and reference numeral 611 denotes a second field. The imagesignal 603 is inverted in polarity at the transition between the firstand second fields in such a manner that the image signal during thesecond field becomes opposite to that during the first field about theamplitude center voltage 605 of the image signal. Reference numeral 604denotes the voltage on the pixel electrode, and the difference betweenthe voltage on the pixel electrode and the voltage on the common voltageis applied across the liquid crystal. During the selection period 608,the image signal 606 is applied to the pixel electrode via the thin filmtransistor, and thus the voltage on the pixel electrode becomes equal tothe image signal 606. However, during the selection period 608, a chargeis stored in a parasitic capacitor between the drain and gate electrodesof the thin film transistor, and this charge flows into the pixelelectrode during the non-selection period 609. This causes a reductionin the voltage of the pixel electrode by an amount of ΔV. To compensatefor the above-described voltage reduction, the voltage 606 of the commonelectrode is lowered by an amount of ΔV from the amplitude centervoltage 605 of the image signal. Thus, the voltage of the pixelelectrode is inverted in polarity every field such that the positive andnegative signals are substantially symmetric to each other about thevoltage of the common electrode. An additional storage capacitor may beformed in the pixel area in such a manner that the storage capacitor isconnected in parallel to the liquid crystal capacitor 706. The storagecapacitor may be formed in the periphery of the pixel area shown in FIG.5 by making an overlap between the pixel electrode 501 and the commonelectrode 502 via the insulating film.

[0053] In the liquid crystal device according to the present embodiment,as shown in FIG. 8, the light-shielding chromium film 807 (101 inFIG. 1) of the upper glass substrate 801 (104 in FIG. 1) is electricallyconnected via a silver paste 805 to the common electrode 808 (111 inFIG. 1) formed on the lower glass substrate 802 (109 in FIG. 1) so thatthey are maintained at the same voltage. FIG. 8a is a plane view of theliquid crystal panel and FIG. 8b is an enlarged cross-sectional viewillustrating a part in which the upper and lower substrates areelectrically connected to each other via the silver paste. In FIG. 8,the light-shielding chromium film shields such areas between the thinfilm transistors and the pixels in the pixel area 803. Thelight-shielding film may also have a part in the periphery 804 whereinit extends between the seal element 806 and the pixel area 803 andextends around the pixel area 803 so that such the part of thelight-shielding chromium film serves to part the pixel area.

[0054] The light-shielding film 807 (101) extending outside the sealingarea in the periphery 804 are electrically connected to the commonelectrode 808 (111) extending from the pixel area, via a silver paste805 at four points outside the sealing area 806 of the liquid crystal(wherein the sealing area is located around the pixel area 803 andserves to seal the pair of substrates). The reason for making theelectrical connections between the light-shielding film and the commonelectrode at a plurality of points is to obtain an uniform voltagedistribution across the light-shielding film over the entire pixel area.

[0055] In FIG. 8b, A terminal extending from the common electrode 808 iselectrically connected via an anisotropic conducting film 809 to aninterconnecting electrode 811 for supplying the common electrodevoltage, wherein the interconnecting electrode 811 is formed on aflexible tape 810 which is used to mount a liquid crystal driver circuitor connect the liquid crystal panel to a circuit board.

[0056] The liquid crystal device constructed in the above-describedmanner was subjected to an electrostatic voltage test under applicationof about 1 kV. Without encountering electrostatic charging, ahigh-quality image was displayed, and no disturbance in the liquidcrystal orientation was observed.

[0057] In the liquid crystal device constructed in the above-describedmanner according to the first embodiment described above, the chromiumfilm serving as the light-shielding metal film is maintained at thefixed voltage (the common electrode voltage). This ensures that thecolor filter substrate is prevented from being electrostatically chargedand thus a high-quality image can be displayed. If the color filtersubstrate had no light-shielding metal film maintained at the fixedvoltage, the electrostatic charge would produce a great voltagedifference between the upper substrate and the pixel electrodes andcommon electrodes formed on the lower substrate. The liquid crystalwould respond to that voltage. Therefore, to achieve a high-qualityimage, it is important that the light-shielding metal film be formed onthe color filter substrate having no electrode for driving the liquidcrystal and be maintained at a fixed voltage. In the present embodiment,since the light-shielding metal film is maintained at the commonelectrode voltage which exists in the liquid crystal device, there is noneed to produce an additional voltage and therefore theanti-electrostatic charge measure can be taken at low cost.

[0058] (Second Embodiment)

[0059] In this second embodiment, as shown in FIG. 9, the liquid crystaldevice has a similar structure to that employed in the first embodimentexcept that the light-shielding chromium film 903 formed on the upperglass substrate (101 in FIG. 1) is grounded. The structure of the liquidcrystal device is described in further detail below with reference toFIG. 9. FIG. 9a is a plane view of a liquid crystal panel, and FIG. 9bis an enlarged cross-sectional view illustrating a part in which anelectric connection between the upper and lower substrates is made via asilver paste. The light-shielding chromium film 903 formed on the innersurface of the upper substrate 901 (104 in FIG. 1) is connected to adummy electrode 904 formed on the inner surface of the lower substrate902 (109 in FIG. 1) wherein the connection is made via the silver paste905 and at a point outside the seal area 906. As shown in FIG. 9b, thedummy electrode 904 is electrically connected via an anisotropicconducting film (ACF) 907 to an interconnecting electrode 908 forsupplying the ground voltage, wherein the interconnecting electrode 908is formed on a flexible circuit board for mounting a liquid crystaldriver thereon or for electrically connecting the liquid crystal panelto a circuit board, thereby connecting the dummy electrode 904 to aground voltage line provided on the liquid crystal driver circuit board.The liquid crystal device constructed in the above-described manner wassubjected to an electrostatic voltage test under an application of about1 kV. Without encountering electrostatic charging, a high-quality imagewas displayed, and no disturbance in the liquid crystal orientation wasobserved.

[0060] In the liquid crystal device constructed in the above-describedmanner according to the second embodiment described above, the chromiumfilm serving as the light-shielding metal film is maintained at thefixed voltage (the ground voltage). This ensures that the color filtersubstrate is prevented from being electrostatically charged and thus ahigh-quality image can be displayed.

[0061] If the light-shielding chromium film is maintained at the groundvoltage, a slight voltage difference can occur between thelight-shielding chromium film and the pixel electrode or the commonelectrode. However, because the color filter layer and the orientatingfilm exist on the light-shielding chromium film, the slight voltagedifference is further decreased by a voltage drop in the color filterlayer and the orientating film. Therefore, the voltage differenceactually applied to the liquid crystal is small enough and it can beneglected. If there were no light-shielding chromium film maintained ata fixed voltage, as high a voltage as a few ten thousand voltages wouldbe applied to the liquid crystal when the color filter substrate waselectrostatically charged, and the liquid crystal device would no longeroperate properly. Therefore, to achieve a high-quality image, it isimportant that the light-shielding metal film be formed on the colorfilter substrate having no electrode for driving the liquid crystal andbe maintained at the fixed voltage (ground voltage). Since the groundvoltage is already present in the liquid crystal device, there is noneed to produce an additional voltage and therefore a liquid crystaldevice having strong resistance to electrostatic charges can be realizedat low cost.

[0062] (Third Embodiment)

[0063] In this third embodiment, the liquid crystal device has a similarstructure to that employed in the first embodiment except that thelight-shielding chromium film formed on the upper glass substrate isconnected to the amplitude center voltage (605 in FIG. 6) of the imagesignal. The connection is made in the same manner as shown in FIG. 9,and the dummy electrode 904 is connected to a voltage line for supplyingthe amplitude center voltage of the image signal wherein the voltageline is formed on a flexible circuit board 909 mounted on the liquidcrystal panel. The liquid crystal device constructed in theabove-described manner was subjected to an electrostatic voltage testunder an application of about 1 kV. Without encountering electrostaticcharging, a high-quality image was displayed, and no disturbance in theliquid crystal orientation was observed.

[0064] In the liquid crystal device constructed in the above-describedmanner according to the third embodiment described above, the chromiumfilm serving as the light-shielding metal film is maintained at thefixed voltage (the amplitude center voltage of the image signal). Forthe same reason as that in the first and second embodiments, the colorfilter substrate is prevented from being electrostatically charged and ahigh-quality image can be obtained. Since the common electrode voltageis already present in the liquid crystal device, there is no need toproduce an additional voltage.

[0065] (Fourth Embodiment)

[0066] In this fourth embodiment, the liquid crystal device has asimilar structure to that employed in the first embodiment except thatthe non-selection voltage supplied via the scanning signal line (503 inFIG. 5) is applied to the light-shielding chromium film formed on theupper glass substrate (wherein the non-selection voltage is suppliedover the scanning signal line 607 in FIG. 6 during the non-selectionperiod 609). The connection is made in the same manner as shown in FIG.9, and the dummy electrode 904 is connected to a voltage line forsupplying the non-selection voltage via the scanning signal line formedon the flexible circuit board 909 mounted on the liquid crystal panel.The liquid crystal device constructed in the above-described manner wassubjected to an electrostatic voltage test under application of about 1kV. Without encountering electrostatic charging, a high-quality imagewas displayed, and no disturbance in the liquid crystal orientation wasobserved.

[0067] In the liquid crystal device constructed in the above-describedmanner according to the fourth embodiment described above, the chromiumfilm serving as the light-shielding metal film is maintained at thefixed voltage (the non-selection voltage of the scanning signal). Forthe same reason as that in the first and second embodiments, the colorfilter substrate is prevented from being electrostatically charged and ahigh-quality image can be achieved. Since the non-selection voltage ofthe scanning signal is already present in the liquid crystal device,there is no need to produce an additional voltage.

[0068] (Fifth Embodiment)

[0069] In this fifth embodiment, the liquid crystal device has a similarstructure to that employed in the first embodiment except that thelight-shielding chromium film formed on the upper glass substrate isconnected to the logic voltage generated in the liquid crystal drivercircuit. The connection is made in the same manner as shown in FIG. 9,and the dummy electrode is connected to a logic voltage line formed onthe flexible circuit board 909 mounted on the liquid crystal panel. Theliquid crystal device constructed in the above-described manner wassubjected to an electrostatic voltage test under an application of about1 kV. Without encountering electrostatic charging, a high-quality imagewas displayed, and no disturbance in the liquid crystal orientationwas-observed.

[0070] In the liquid crystal device constructed in the above-describedmanner according to the fifth embodiment described above, the chromiumfilm serving as the light-shielding metal film is maintained at thefixed voltage (the logic voltage). For the same reason as that in thefirst and second embodiments, the color filter substrate is preventedfrom being electrostatically charged and a high-quality image can beachieved. Since the logic voltage is already present in the liquidcrystal device, there is no need to produce an additional voltage.Although a chromium film is employed as the light-shielding film in thisfifth embodiment, it has been confirmed experimentally that a film ofmetal other than Cr, such as Ta, Al, Au, may also be employed for thesame purpose.

[0071] (Sixth Embodiment)

[0072]FIG. 2a is a schematic diagram illustrating a main part of aliquid crystal device according to the sixth embodiment of theinvention. The structure is described first. Two transparent glasssubstrates 203 and 210 with a thickness of 1.1 mm are disposed in closeproximity to each other, and a liquid crystal layer 207 is disposedbetween them. A red/green/blue (RGB) color filter 204, a light-shieldingresin film 205, and an orientating film 206 are formed one on another onthe inner surface of the upper glass substrate 203. A transparentconducting ITO film 202 and a polarizing plate 201 are formed on theouter surface of the upper glass substrate 203. Common electrodes 213,an insulating layer 209, pixel electrodes 212 and an orientating film208 are formed on the inner surface of the lower glass substrate 210,and a polarizing plate 211 is formed on the outer surface.

[0073] As described earlier with reference to the plane view of thelower glass substrate shown in FIG. 5, scanning signal lines (gatelines) 503 and image signal lines (source lines) 504 extend in a matrixform across the respective pixels. Thin film transistors (TFTs) 505 areformed near the respective intersections of the scanning signal lines503 and the image signal lines 504, wherein the gate electrodes of therespective thin film transistors are connected to the correspondingscanning signal lines 503, the source electrodes to the correspondingimage signal lines 504, and the drain electrodes to the correspondingpixel electrodes 501 (212). In this sixth embodiment, the driving isperformed in the same manner as in the first embodiment.

[0074] In FIG. 2, the common electrode 213 and the pixel electrode 212in one pixel are located in different layers separated by the insulatinglayer 209. In FIG. 2a, lines 214 denote the direction of the electricfield. In this embodiment, the gap between the upper and lowersubstrates, the distance between electrodes, and the rubbing directionare slightly different from those employed in the first embodiment. Thatis, in this sixth embodiment, the upper and lower substrates were spacedby 4.0 μm, and a nematic liquid crystal having positive dielectricanisotropy and having anisotropy in refractive index Δn=0.070 wasemployed as the liquid crystal material 207. The line-shaped commonelectrodes 213 and the pixel electrodes 212 were spaced by 15 μm whereinthe width was set to 5 μm for both electrodes. A rubbing orientationprocess was performed so that the longitudinal axes of the liquidcrystal molecules were aligned at 45° with respect to the longitudinaldirection of the line-shaped electrodes (common electrodes 213, pixelelectrodes 212). The polarizing plate 201 on the upper glass substrate203 was disposed such that its absorption axis became parallel to theorientation of the liquid crystal. On the other hand, the polarizingplate 211 on the lower glass substrate 210 was disposed such that itsabsorption axis became perpendicular to the orientation of the liquidcrystal. In this state, black is displayed in the pixel. The orientationangle of the liquid crystal molecules varies in response to a voltageapplied from external driving means. Thus, it is possible to control thebrightness by changing the applied voltage. Below the lower substrate210, there is provided a back light source.

[0075] As shown in FIG. 2a, the light-shielding film 205 is disposed sothat the areas in which the thin film transistors, the image signallines, and the scanning signal lines formed on the lower substrate areshielded from light.

[0076] In the present embodiment, the transparent conducting ITO film202 formed on the upper glass substrate 203 is connected to the groundvoltage via an electric interconnection passing through an area otherthan the pixel area.

[0077]FIG. 3 is a plane view illustrating a liquid crystal panel. InFIG. 3, reference numeral 302 denotes the lower substrate (correspondingto 210 in FIG. 2a), 301 denotes the upper substrate (203 in FIG. 2a),303 denotes the pixel area, and 304 denotes the periphery of the pixelarea. In the present embodiment, the transparent conducting film 202 isformed on the outer surface of the upper substrate, in the areaincluding the pixel area 303 and its periphery 304.

[0078] The connection of the transparent conducting film and to theground voltage may be made as follows. The transparent conducting filmis exposed at the end of the periphery and the exposed portion iscontacted or connected via a connection member to a metal enclosure (notshown) so that the transparent conducting film is maintained at a fixedvoltage (ground voltage). If the metal enclosure is maintained at afixed voltage (ground voltage), the enclosure itself has theelectrostatic shielding capability. This further ensures that the liquidcrystal device is protected from electrostatic charges. The manner ofconnecting the transparent conducting film to the ground voltage is notlimited to the above specific method, but the connection may be realizedin various fashions.

[0079] The liquid crystal device constructed in the above-describedmanner was subjected to an electrostatic voltage test under anapplication of about 1 kV.

[0080] Without encountering electrostatic charging, a high-quality imagewas displayed. In the liquid crystal device constructed in theabove-described manner according to the sixth embodiment describedabove, the color filter substrate is prevented from beingelectrostatically charged and thus it is possible to display ahigh-quality image. Since the ground voltage is already present in theliquid crystal device, there is no need to produce an additionalvoltage.

[0081] Although in the present embodiment the transparent conducting ITOfilm is maintained at the ground voltage, it may also be maintained, asin the second through fifth embodiment, at another voltage such as thecommon electrode voltage, the center voltage of the image signalamplitude, the non-selection voltage of the scanning signal, or thelogic voltage provided from an external driving means. Furthermore,instead of the ITO film, other materials such as SnO₂ may also beemployed to form the transparent conducting film. It is not necessarilyrequired that the transparent conducting film be formed over the entirearea of the upper substrate, but it may be formed in a partial fashion.

[0082] (Seventh Embodiment)

[0083] In this seventh embodiment, the transparent conducting ITO filmformed on the upper substrate in the sixth embodiment described above isreplaced by a chromium film, wherein the chromium film is formed in theperipheral area 304 other than the pixel area 303. The chromium filmformed on the upper glass substrate is maintained at the ground voltage.The chromium film in the peripheral area 304 may also serve as a partingplate for shielding the periphery of the pixel area 303 from light. Asin the sixth embodiment, the chromium film may be connected to anyvoltage selected from various voltages available. The liquid crystaldevice constructed in the above-described manner was subjected to anelectrostatic voltage test under an application of about 1 kV. Withoutencountering electrostatic charging, a high-quality image was displayed,and no disturbance in the liquid crystal orientation was observed.

[0084] In the liquid crystal device constructed in the above-describedmanner according to the seventh embodiment described above, the colorfilter substrate is prevented from being electrostatically charged andthus a high-quality image can be displayed. Since the common electrodevoltage is already present in the liquid crystal device, there is noneed to produce an additional voltage.

[0085] Although in the present embodiment the chromium is maintained atthe ground voltage, it may also be maintained at another voltage such asthe common electrode voltage, the center voltage of the image signal,the non-selection voltage of the scanning signal, or the logic voltageprovided from an external driving means. A high-quality image can beobtained regardless of which voltage the chromium film is maintained at.

[0086] Although in the present embodiment the chromium film is formed onthe outer surface of the liquid crystal panel substrate, in the areaexcept for the pixel area, the chromium film may also be forming in theperipheral area of the inner surface of the liquid crystal panelsubstrate (wherein the thin film transistors and the areas betweenpixels in the pixel area are shielded by the light-shielding resin film,in the present embodiment).

[0087] Although a chromium film is employed in the present embodiment,it has been confirmed experimentally that a film of metal other than Cr,such as Ta, Al, Au, may also be employed for the same purpose.

[0088] (Eighth Embodiment)

[0089] This eighth embodiment is obtained by modifying the structureemployed in the sixth embodiment described above with reference to FIG.2a. In this eighth embodiment, the upper and lower substrates werespaced by 4.0 μm, and a nematic liquid crystal having positivedielectric anisotropy and having anisotropy in refractive index Δn=0.070was employed as the liquid crystal material 207. The line-shaped commonelectrodes 213 and the pixel electrodes 212 were spaced by 15 μm whereinthe width was set to 10 μm for both electrodes. A rubbing orientationprocess was performed so that the longitudinal axes of the liquidcrystal molecules were aligned at 45° with respect to the longitudinaldirection of the line-shaped electrodes (common electrodes 213, pixelelectrodes 212). The polarizing plate 201 on the upper glass substrate203 was disposed such that its absorption axis became parallel to theorientation of the liquid crystal. On the other hand, the polarizingplate 211 on the lower glass substrate 210 was disposed such that itsabsorption axis became perpendicular to the orientation of the liquidcrystal. In this state, black is displayed in the pixel. The orientationangle of the liquid crystal molecules varies in response to a voltageapplied from external driving means. Thus, it is possible to control thebrightness by changing the applied voltage. Below the lower substrate210, there is provided a back light source.

[0090] In the present embodiment, the transparent conducting ITO film202 formed on the upper glass substrate 203 is not connected to any partand it is maintained in an electrically floating state.

[0091] The liquid crystal device constructed in the above-describedmanner was subjected to an electrostatic voltage test under anapplication of about 1 kV. Without encountering electrostatic charging,a high-quality image was displayed.

[0092] In the liquid crystal device constructed in the above-describedmanner according to the eighth embodiment described above, the colorfilter substrate is prevented from being electrostatically charged andthus a high-quality image can be displayed. Furthermore, since thevoltage of the transparent conducting film is maintained in theelectrically floating state, no electric connection is needed. Thismakes it possible to take the anti-electrostatic charge measure at lowcost.

[0093] (Ninth Embodiment)

[0094]FIG. 2b is a schematic diagram illustrating a main part of aliquid crystal device according to the sixth embodiment of theinvention. The structure is described first. Two transparent glasssubstrates 216 and 224 with a thickness of 1.1 mm are disposed in closeproximity to each other, and a liquid crystal layer 221 is disposedbetween them. A red/green/blue (RGB) color filter 218, a light-shieldingresin film 217, a transparent conducting ITO film 219, and anorientating film 220 are formed one on another on the inner surface ofthe upper glass substrate 216, and a polarizing plate 215 is disposed onthe outer surface of the upper glass substrate 216. Common electrodes227, an insulating layer 223, pixel electrodes 228, and an orientatingfilm 222 are formed on the inner surface of the lower glass substrate224, and a polarizing plate 225 is disposed on the outer surface of thelower glass substrate 224.

[0095] As described earlier with reference to the plane view of thelower glass substrate shown in FIG. 5, scanning signal lines (gatelines) 503 and image signal lines (source lines) 504 extend in a matrixform across the respective pixels. Thin film transistors (TFTs) 505 areformed near the respective intersections of the scanning signal lines503 and the image signal lines 504, wherein the drain electrodes of therespective thin film transistors are connected to the correspondingpixel electrodes 501 (228). In this ninth embodiment, the driving isperformed in the same manner as in the first embodiment.

[0096] The common electrode 227 and the pixel electrode 228 in one pixelare located in different layers separated by the insulating layer 223.In FIG. 2b, lines 226 denote the direction of the electric field. Inthis embodiment, the gap between the upper and lower substrates, theanisotropy of refractive index, the distance between electrodes, and therubbing direction are slightly different from those employed in thefirst embodiment. That is, the upper and lower substrates were spaced by4.0 μm, and a nematic liquid crystal having positive dielectricanisotropy and having anisotropy in refractive index Δn=0.085 wasemployed as the liquid crystal material 221. The line-shaped commonelectrodes 227 and the pixel electrodes 228 were spaced by 12 μm whereinthe width was set to 5 μm for both electrodes. A rubbing orientationprocess was performed so that the longitudinal axes of the liquidcrystal molecules were aligned at 40° with respect to the longitudinaldirection of the line-shaped electrodes (common electrodes 227, pixelelectrodes 228). The polarizing plate 215 on the upper glass substrate216 was disposed such that its absorption axis became parallel to theorientation of the liquid crystal. On the other hand, the polarizingplate 225 on the lower glass substrate 224 was disposed such that itsabsorption axis became perpendicular to the orientation of the liquidcrystal. In this state, black is displayed in the pixel. The orientationangle of the liquid crystal molecules varies in response to a voltageapplied from external driving means. Thus, it is possible to control thebrightness by changing the applied voltage. Below the lower substrate224, there is provided a back light source.

[0097] As shown in FIG. 2a, the light-shielding film 205 is disposed sothat the areas in which the thin film transistors, the image signallines, and the scanning signal lines formed on the lower substrate areshielded from light.

[0098] In the present embodiment, the transparent conducting ITO film219 formed on the upper glass substrate 216 is not connected to any partand it is maintained in an electrically floating state. The liquidcrystal device constructed in the above-described manner was subjectedto an electrostatic voltage test under an application of about 1 kV.Without encountering electrostatic charging, a high-quality image wasdisplayed, and no disturbance in the liquid crystal orientation wasobserved.

[0099] In the liquid crystal device constructed in the above-describedmanner according to the ninth embodiment described above, the colorfilter substrate is prevented from being electrostatically charged andthus a high-quality image can be displayed. Furthermore, since thevoltage of the transparent conducting film is maintained in a floatingstate, no electrical connection is required. This makes it possible totake the anti-electrostatic charge measure at low cost. In general, if atransparent conducting film is formed on the surface which is in contactwith the liquid crystal, that is, in the inside of a liquid crystalcell, a voltage difference occurs between the transparent conductingfilm and the pixel electrode and/or the common electrode. As a result,degradation in the image quality occurs. However, in the presenttechnique, since the voltage of the conductive film is maintained in thefloating state, the degradation in the image quality is suppressed.

[0100] Although in this embodiment the transparent conducting ITO filmis formed between the color filter layer and the orientating film on theupper substrate, it may also be formed between the substrate and thecolor filter layer.

[0101] (Tenth Embodiment)

[0102] In this embodiment, the light-shielding resin film 205 or 217employed in the eighth or ninth embodiment described above withreference to FIG. 2 is replaced by a light-shielding film made up ofmetal such as chromium. The light-shielding metal film is used not onlyto shield the thin film transistors and the areas between adjacentpixels from light, but also to provide at periphery of the pixel area anelectrical connection for supplying a fixed voltage as described abovewith reference to the first embodiment through the fifth embodiment inconjunction with FIG. 8.

[0103] Alternatively, a transparent conductive ITO film in anelectrically floating state such as that employed in the eighth andninth embodiments is formed on the outer or inner surface of the uppersubstrate as shown in FIG. 2 so that the transparent conducting ITO filmin the electrically floating state is combined with the light-shieldingchromium film.

[0104] In this structure, the transparent conducting ITO film in theelectrically floating state absorbs electrostatic charges and thelight-shielding metal film shields the liquid crystal from electrostaticcharges. Therefore, this structure provides higher resistance toelectrostatic charges.

[0105] However, when the light shielding metal film and the transparentconducting film are formed into a multilayer structure on the innersurface of the upper substrate, it is required that these two layersshould be isolated by a color filter or other an insulating film.

[0106] Although in the present embodiment the transparent conducting ITOfilm is formed between the color filter layer and the orientating filmon the upper substrate, it may also be formed between the substrate andthe color filter layer.

[0107] (Eleventh Embodiment)

[0108] In this eleventh embodiment, instead of the transparentconducting ITO film employed in the liquid crystal device according tothe eighth or ninth embodiment, a chromium film is formed on the outeror inner surface of the upper glass substrate, in the periphery 304 ofthe pixel area 303 as shown in FIG. 3. The voltage of the chromium filmformed on the upper glass substrate is maintained in a floating state.

[0109] The liquid crystal device constructed in the above-describedmanner was subjected to an electrostatic voltage test under anapplication of about 1 kV. Without encountering electrostatic charging,a high-quality image was displayed, and no disturbance in the liquidcrystal orientation was observed.

[0110] In the liquid crystal device constructed in the above-describedmanner according to the eleventh embodiment described above, the colorfilter substrate is prevented from being electrostatically charged andthus a high-quality image can be displayed. Furthermore, since thevoltage of the chromium film is maintained in the floating state, noelectrical connection is required. This makes it possible to take theanti-electrostatic charge measure at low cost. Furthermore, thelight-shielding film may also serve to part the pixel area.

[0111] In the present embodiment of the invention, as described above,it is possible to realize a liquid crystal device capable of displayinga high-quality image without encountering significant influence ofelectrostatic charges.

[0112] (Twelfth Embodiment)

[0113] In this twelfth embodiment, the upper polarizing plate 103, 201,or 215 shown in FIG. 1b, 2 a or 2 b is modified to have electricalconductivity. Such a polarizing plate may be easily realized by mixingconductive particles in a film material used to form the polarizingplate or by bonding a transparent conducting film to a polarizing film.

[0114] The conductive polarizing plate may be maintained either in anelectrically floating state or at a particular fixed voltage (such asthe common electrode voltage, ground voltage, non-selection scanningsignal voltage, logic voltage supplied from an external driving means).When the conductive polarizing plate is maintained at a fixed voltage,the polarizing plate or the conductive polarizing plate is exposed andit is connected to the fixed voltage in a similar manner to thatemployed in the sixth embodiment.

[0115] The liquid crystal device constructed in the above-describedmanner was subjected to an electrostatic voltage test under anapplication of about 1 kV. Without encountering electrostatic charging,a high-quality image was displayed, and no disturbance in the liquidcrystal orientation was observed.

[0116] In the liquid crystal device of the present embodiment, the colorfilter substrate is prevented from being electrostatically charged andthus a high-quality image can be displayed.

[0117] In addition to the upper polarizing plate, the lower polarizingplate may also be formed into the conductive fashion so that the liquidcrystal panel is disposed between the upper and lower conductivepolarizing plates thereby achieving higher resistance to electrostaticcharges.

[0118] The technique of the present embodiment may be combined with anytechnique disclosed above in the first through eleventh embodiments soas to realize a liquid crystal panel having higher resistance toelectrostatic charges.

[0119] (Thirteenth Embodiment)

[0120] An electronic equipment using a liquid crystal device based onany technique disclosed above in the first through twelfth embodimentsis described below.

[0121] As shown in FIG. 10, this electronic equipment using a liquidcrystal display device includes an information source 1000 forgenerating information to be displayed, a processing circuit 1002 forprocessing the information to be displayed, a driving circuit 1004 fordriving the display panel, a display panel 1006 such as a liquid crystalpanel, a clock generator 1008, and a power supply 1010. The informationsource 1000 for generating information to be displayed includes a memorysuch as ROM and RAM, and a tuner circuit for selecting a desiredtelevision signal and outputting the selected signal. In response to theclock signal generated by the clock generator 1008, the informationsource 1000 outputs information such as a video signal to be displayed.The processing circuit 1002 processes the information to be displayed inresponse to the clock signal generated by the clock generator 1008, andoutputs the resultant signal. The processing circuit 1002 includes forexample an amplifier, an inverter, a phase developing circuit, arotating circuit, a gamma correction circuit, and a clamping circuit.The driving circuit 1004 for driving the liquid crystal panel 1006includes a scanning driver circuit and a data driver circuit. The powersupply 1010 supplies electric power to the respective circuit elementsdescribed above.

[0122] Specific examples of an electronic equipment include a personalcomputer(PC) capable of handling multimedia data or an engineering workstation (EWS) such as that shown in FIG. 11, a pager such as that shownin FIG. 12, and a portable telephone, a word processor, a televisionreceiver, a video tape recorder with a view-finder or a monitor display,a pocket-sized electronic notebook, a calculator, a car navigationsystem, a POS terminal, and other devices with a touch panel.

[0123] The personal computer 1200 shown in FIG. 11 consists of a mainpart 1204 including a key board 1202 and a liquid crystal display 1206.The pager 1300 shown in FIG. 12 consists of a metal frame 1302 and otherelements located inside the metal frame 1302, including a glasssubstrate 1304, a light guide 1306 with a back light 1306 a, a circuitboard 1308, first and second shield plates 1310 and 1312, two elasticconductors 1314 and 1316, and a film carrier tape (flexible substrate)1318. The two elastic conductors 1314 and 1316 and the film carrier tape1318 are used to connect the glass substrate 1304 to the circuit board1308.

[0124] The liquid crystal display panel 1304 consists of two transparentplates 1304 a and 1304 b and a liquid crystal sealed between thesetransparent plates thereby forming at least a liquid crystal displaypanel. On one of the transparent plates, there may be a driving circuit1004 and also an information processing circuit 1002, such as thoseshown in FIG. 10. Other circuits which cannot be mounted on the liquidcrystal display panel 1304 may be disposed externally for example on thecircuit board 1308 as shown in FIG. 12.

[0125] In the case of a pager such as that shown in FIG. 12, a circuitboard 1308 is needed in addition to a glass substrate 1304. However, ingeneral applications in which a liquid crystal display panel is used asan electronic component, a liquid crystal panel having the abovestructure 1304 can be used as an unit component. A substrate 1304 may bedisposed in a metal frame 1302 serving as a case, and the resultantstructure may be used as an electronic component functioning as a liquidcrystal display device. Furthermore, in the case of the back light type,a liquid crystal display device may be constructed by disposing asubstrate 1304 and a light guide 1306 including a back light 1306 a in ametal frame 1302. FIG. 13 illustrates another example of an electroniccomponent functioning as a liquid crystal display device. In this case,a substrate 1304 is formed with two transparent substrates 1304 a and1304 b, and a TCP (tape carrier package) 1320 is connected to one of thetransparent substrates. The TCP 1320 includes a polyimide tape 1322 onwhich a metal interconnection conducting film is formed.

[0126] Although the present invention is described above with referenceto preferred embodiments, the invention is not limited to thoseembodiments. Various modifications may be made without departing fromthe spirit and scope of the invention.

[0127] In connection with the techniques disclosed in the first throughtwelfth embodiments, various fixed voltages are supplied from the powersupply 1010 shown in FIG. 10 to the liquid crystal device. The fixedvoltage applied to the light-shielding film or the transparentconducting film may be supplied from the above power supply or thedriving circuit 1004. As described earlier with reference to specificembodiments, the light-shielding film is connected to the commonelectrode or the dummy electrode. The common electrode or the dummyelectrode may be connected to a proper fixed voltage via a tape 1318shown in FIG. 12 or a tape 1322 shown in FIG. 13.

[0128] When a fixed voltage is applied to the transparent conductivefilm or a metal film formed on the outer surface of the upper glasssubstrate, the fixed voltage may be supplied from the power supply 1010shown in FIG. 10 to the frame 1302 shown in FIG. 12 serving as the metalenclosure so that the fixed voltage is applied via the frame 1302 to thetransparent conducting film or the metal film formed on the uppersubstrate 1304 a.

[0129] In the embodiments described above, chromium is employed to formthe metal film. Alternatively, Ta, Al, Au, a Cr—Ni alloy, or a Cr—Cualloy may also be employed for the same purpose. Furthermore, instead ofITO, other materials such as SnO₂ may also be employed to form thetransparent conducting film. It is not necessarily required that thetransparent conducting film be formed over the entire surface but it maybe formed in a partial fashion.

[0130] Industrial Applicability

[0131] As described above, the present invention provides an activematrix type liquid crystal device capable of displaying a high-qualityimage over a large viewing angle. The liquid crystal device according tothe invention may be used as a display device in a wide variety ofelectronic applications such as a personal computer, work station, etc.,and also as a monitor device in a multimedia terminal device, televisionset, etc. The liquid crystal device according to the invention isparticularly useful when it is used in an environment whereelectrostatic charging often occurs for example in an office where therea large number of electronic apparatus.

1. A liquid crystal device comprising a pair of substrates, a liquidcrystal disposed between said pair of substrates, one of said substrateshaving, thereon, scanning signal lines and image signal lines disposedin a matrix form, active elements connected to the respective scanningsignal lines and image signal lines, a pixel electrode connected to therespective active elements, and a common electrode, thereby making itpossible to apply an electric field across the liquid crystal disposedbetween each said pixel electrode and said common electrode in such amanner that said electric field is applied in a direction substantiallyparallel to the plane of said substrates, wherein a light-shieldingmetal film is formed on the other-side substrate opposite to said one ofthe substrate, and a fixed voltage is applied to said light-shieldingmetal film.
 2. A liquid crystal device including a pair of substrates, aliquid crystal disposed between said pair of substrates, one of thesubstrates having, thereon, scanning signal lines and image signal linesdisposed in a matrix form, active elements connected to the respectivescanning signal lines and image signal lines, a pixel electrodeconnected to the respective active elements, and a common electrode,thereby making it possible to apply an electric field across the liquidcrystal disposed between each said pixel electrode and said commonelectrode in such a manner that said electric field is applied in adirection substantially parallel to the plane of said substrates,wherein a transparent conducting film is formed on the other-sidesubstrate opposite to said one of the substrate, and a fixed voltage isapplied to said transparent conducting film.
 3. A liquid crystal deviceincluding a pair of substrates, a liquid crystal disposed between saidpair of substrates, one of the substrates having, thereon, scanningsignal lines and image signal lines disposed in a matrix form, activeelements connected to the respective scanning signal lines and imagesignal lines, a pixel electrode connected to the respective activeelements, and a common electrode, thereby making it possible to apply anelectric field across the liquid crystal disposed between each saidpixel electrode and said common electrode in such a manner that saidelectric field is applied in a direction substantially parallel to theplane of said substrates, wherein a conductive film is formed on theother-side substrate opposite to said one of the substrate, in theperiphery of the pixel area on either the inner surface or the outersurface of said other-side substrate, and a fixed voltage is applied tosaid conductive film.
 4. A liquid crystal device including a pair ofsubstrates, a liquid crystal disposed between said pair of substrates,one of the substrates having, thereon, scanning signal lines and imagesignal lines disposed in a matrix form, active elements connected to therespective scanning signal lines and image signal lines, a pixelelectrode connected to the respective active elements, and a commonelectrode, thereby making it possible to apply an electric field acrossthe liquid crystal disposed between each said pixel electrode and saidcommon electrode in such a manner that said electric field is applied ina direction substantially parallel to the plane of said substrates,wherein a polarizing plate having an electrical conductivity is disposedon the outer surface of said other-side substrate opposite to said onesubstrate, and a fixed voltage is applied to said polarizing plate.
 5. Aliquid crystal device according to claim 1 , wherein said fixed voltageis either a ground voltage, a voltage equal to the voltage on saidcommon voltage, the center voltage of an image signal supplied over saidimage signal lines, a non-selection voltage of a scanning signal appliedover said scanning signal lines, a logic voltage supplied from drivingmeans for driving said liquid crystal device.
 6. A liquid crystal deviceaccording to claim 2 , wherein said fixed voltage is either a groundvoltage, a voltage equal to the voltage on said common voltage, thecenter voltage of an image signal supplied over said image signal lines,a non-selection voltage of a scanning signal applied over said scanningsignal lines, a logic voltage supplied from driving means for drivingsaid liquid crystal device.
 7. A liquid crystal device according toclaim 3 , wherein said fixed voltage is either a ground voltage, avoltage equal to the voltage on said common voltage, the center voltageof an image signal supplied over said image signal lines, anon-selection voltage of a scanning signal applied over said scanningsignal lines, a logic voltage supplied from driving means for drivingsaid liquid crystal device.
 8. A liquid crystal device according toclaim 4 , wherein said fixed voltage is either a ground voltage, avoltage equal to the voltage on said common voltage, the center voltageof an image signal supplied over said image signal lines, anon-selection voltage of a scanning signal applied over said scanningsignal lines, a logic voltage supplied from driving means for drivingsaid liquid crystal device.
 9. A liquid crystal device including a pairof substrates, a liquid crystal disposed between said pair ofsubstrates, one of the substrates having, thereon, scanning signal linesand image signal lines disposed in a matrix form, active elementsconnected to the respective scanning signal lines and image signallines, a pixel electrode connected to the respective active elements,and a common electrode, thereby making it possible to apply an electricfield across the liquid crystal disposed between each said pixelelectrode and said common electrode in such a manner that said electricfield is applied in a direction substantially parallel to the plane ofsaid substrates, wherein a transparent conducting film is formed oneither the inner-side or outer surface of said other-side substrateopposite to said one substrate, and the voltage of the transparentconductive film is maintained in a floating state.
 10. A liquid crystaldevice including a pair of substrates, a liquid crystal disposed betweensaid pair of substrates, one of the substrates having, thereon, scanningsignal lines and image signal lines disposed in a matrix form, activeelements connected to the respective scanning signal lines and imagesignal lines, a pixel electrode connected to the respective activeelements, and a common electrode, thereby making it possible to apply anelectric field across the liquid crystal disposed between each saidpixel electrode and said common electrode in such a manner that saidelectric field is applied in a direction substantially parallel to theplane of said substrates, wherein a conductive film is formed on theother-side substrate opposite to said one of the substrate, in theperiphery of the pixel area on either the inner surface or the outersurface of said other-side substrate, and the voltage of the conductivefilm is maintained in a floating state.
 11. A liquid crystal deviceincluding a pair of substrates, a liquid crystal disposed between saidpair of substrates, one of the substrates having, thereon, scanningsignal lines and image signal lines disposed in a matrix form, activeelements connected to the respective scanning signal lines and imagesignal lines, a pixel electrode connected to the respective activeelements, and a common electrode, thereby making it possible to apply anelectric field across the liquid crystal disposed between each saidpixel electrode and said common electrode in such a manner that saidelectric field is applied in a direction substantially parallel to theplane of said substrates, wherein a polarizing plate having anelectrical conductivity is disposed on the outer surface of saidother-side substrate opposite to said one substrate, and the voltage ofsaid polarizing plate is maintained in a floating state.
 12. Electronicequipment using a liquid crystal display device, said liquid crystaldevice including a pair of substrates, a liquid crystal disposed betweensaid pair of substrates, one of the substrates having, thereon, scanningsignal lines and image signal lines disposed in a matrix form, activeelements connected to the respective scanning signal lines and imagesignal lines, a pixel electrode connected to the respective activeelements, and a common electrode, thereby making it possible to apply anelectric field across the liquid crystal disposed between each saidpixel electrode and said common electrode in such a manner that saidelectric field is applied in a direction substantially parallel to theplane of said substrates, wherein a light-shielding metal film is formedon said other-side substrate opposite to said one of the substrate, andsaid electronic equipment includes: an interconnection through which afixed voltage is applied to said light-shielding metal film; and a powersupply for supplying said fixed voltage via said interconnection. 13.Electronic equipment using a liquid crystal display device, said liquidcrystal device including a pair of substrates, a liquid crystal disposedbetween said pair of substrates, one of the substrates having, thereon,scanning signal lines and image signal lines disposed in a matrix form,active elements connected to the respective scanning signal lines andimage signal lines, a pixel electrode connected to the respective activeelements, and a common electrode, thereby making it possible to apply anelectric field across the liquid crystal disposed between each saidpixel electrode and said common electrode in such a manner that saidelectric field is applied in a direction substantially parallel to theplane of said substrates, wherein a transparent conducting film isformed on the outer surface of said other-side substrate opposite tosaid one of the substrate, and said electronic equipment includes: aframe through which a fixed voltage is applied to said transparentconducting film; and a power supply for supplying said fixed voltage viasaid frame.
 14. Electronic equipment using a liquid crystal displaydevice, said liquid crystal device including a pair of substrates, aliquid crystal disposed between said pair of substrates, one of thesubstrates having, thereon, scanning signal lines and image signal linesdisposed in a matrix form, active elements connected to the respectivescanning signal lines and image signal lines, a pixel electrodeconnected to the respective active elements, and a common electrode,thereby making it possible to apply an electric field across the liquidcrystal disposed between each said pixel electrode and said commonelectrode in such a manner that said electric field is applied in adirection substantially parallel to the plane of said substrates,wherein a conductive film is formed on the inner or outer surface ofsaid other-side substrate opposite to said one of the substrate, saidconductive film being formed in the periphery of a pixel area, and saidelectronic equipment includes: an interconnection or frame through whicha fixed voltage is applied to said conductive film; and a power supplyfor supplying said fixed voltage via said interconnection or frame. 15.Electronic equipment using a liquid crystal display device, said liquidcrystal device including a pair of substrates, a liquid crystal disposedbetween said pair of substrates, one of the substrates having, thereon,scanning signal lines and image signal lines disposed in a matrix form,active elements connected to the respective scanning signal lines andimage signal lines, a pixel electrode connected to the respective activeelements, and a common electrode, thereby making it possible to apply anelectric field across the liquid crystal disposed between each saidpixel electrode and said common electrode in such a manner that saidelectric field is applied in a direction substantially parallel to theplane of said substrates, wherein a polarizing plate is formed on theouter surface of said other-side substrate opposite to said one of thesubstrate, and said electronic equipment includes: an interconnection ora frame through which a fixed voltage is applied to said polarizingplate; and a power supply for supplying said fixed voltage via saidinterconnection or frame.
 16. Electronic equipment according to claim 12, wherein said fixed voltage is either a ground voltage, a voltage equalto the voltage on said common voltage, the center voltage of an imagesignal supplied over said image signal lines, a non-selection voltage ofa scanning signal applied over said scanning signal lines, a logicvoltage supplied from driving means for driving said liquid crystaldevice.
 17. Electronic equipment according to claim 13 , wherein saidfixed voltage is either a ground voltage, a voltage equal to the voltageon said common voltage, the center voltage of an image signal suppliedover said image signal lines, a non-selection voltage of a scanningsignal applied over said scanning signal lines, a logic voltage suppliedfrom driving means for driving said liquid crystal device. 18.Electronic equipment according to claim 14 , wherein said fixed voltageis either a ground voltage, a voltage equal to the voltage on saidcommon voltage, the center voltage of an image signal supplied over saidimage signal lines, a non-selection voltage of a scanning signal appliedover said scanning signal lines, a logic voltage supplied from drivingmeans for driving said liquid crystal device.
 19. Electronic equipmentaccording to claim 15 , wherein said fixed voltage is either a groundvoltage, a voltage equal to the voltage on said common voltage, thecenter voltage of an image signal supplied over said image signal lines,a non-selection voltage of a scanning signal applied over said scanningsignal lines, a logic voltage supplied from driving means for drivingsaid liquid crystal device.
 20. Electronic equipment using a liquidcrystal display device, said liquid crystal device including a pair ofsubstrates, a liquid crystal disposed between said pair of substrates,one of the substrates having, thereon, scanning signal lines and imagesignal lines disposed in a matrix form, active elements connected to therespective scanning signal lines and image signal lines, a pixelelectrode connected to the respective active elements, and a commonelectrode, thereby making it possible to apply an electric field acrossthe liquid crystal disposed between each said pixel electrode and saidcommon electrode in such a manner that said electric field is applied ina direction substantially parallel to the plane of said substrates,wherein a transparent conducting film is formed on either the inner-sideor outer surface of said other-side substrate opposite to said onesubstrate, and the voltage of said transparent conducting film ismaintained in a floating state.
 21. Electronic equipment using a liquidcrystal display device, said liquid crystal device including a pair ofsubstrates, a liquid crystal disposed between said pair of substrates,one of the substrates having, thereon, scanning signal lines and imagesignal lines disposed in a matrix form, active elements connected to therespective scanning signal lines and image signal lines, a pixelelectrode connected to the respective active elements, and a commonelectrode, thereby making it possible to apply an electric field acrossthe liquid crystal disposed between each said pixel electrode and saidcommon electrode in such a manner that said electric field is applied ina direction substantially parallel to the plane of said substrates,wherein a conductive film is formed on the other-side substrate oppositeto said one of the substrate, in the periphery of the pixel area oneither the inner surface or the outer surface of said other-sidesubstrate, and the voltage of said conductive film is maintained in afloating state.
 22. Electronic equipment using a liquid crystal displaydevice, said liquid crystal device including a pair of substrates, aliquid crystal disposed between said pair of substrates, one of thesubstrates having, thereon, scanning signal lines and image signal linesdisposed in a matrix form, active elements connected to the respectivescanning signal lines and image signal lines, a pixel electrodeconnected to the respective active elements, and a common electrode,thereby making it possible to apply an electric field across the liquidcrystal disposed between each said pixel electrode and said commonelectrode in such a manner that said electric field is applied in adirection substantially parallel to the plane of said substrates,wherein a polarizing plate having an electrical conductivity is disposedon the outer surface of said other-side substrate opposite to said onesubstrate, and the voltage of said polarizing plate is maintained in afloating state.